Capacidade de suporte de reservatório de acumulação hidrelétrico na bacia hidrográfica do rio Uberabinha, Triângulo Mineiro

Abstract

Accumulation reservoirs are implemented for various purposes, but the construction of the dam alters the morphology and dynamics of the water body, changes that favor the modification of water quality, which can induce the eutrophication process. In Brazil, as well as in the State of Minas Gerais, standards and indexes are established to ensure the maintenance of water quality. Given this context, this study used the Water Quality Analysis Simulation Program computational tool to model water quality in a stretch of the Uberabinha River, downstream of the urban area of Uberlândia, Triângulo Mineiro, with the objective of evaluating the support capacity of the PCH Malagone hydroelectric reservoir, that is, the maximum pollutant load that the lentic environment can receive without exceeding the environmental limits established by legislation and maintaining the trophic state at the mesotrophic level. Sensitivity analysis and calibration of more sensitive kinetic terms allowed adjustment between mathematical simulations and the parameters dissolved oxygen, biochemical oxygen demand, nitrate, ammonia and total phosphorus monitored at three stations. The results indicate that the accumulation reservoir currently receives organic and nutrient loads greater than its assimilation capacity, compromising the maintenance of water quality. Based on this, reference values were defined to ensure, simultaneously, compliance with class 2 standards and with the mesotrophic trophic state in the studied section, considering four hydrological scenarios: average flow of 45,2606 m³/s; flow of 29,7000 m³/s which results in the reservoir a residence time immediately above 40 days, characterizing it as a lentic environment according to current legislation; minimum reference flow Q7,10 equal to 6,2274 m³/s; and critical or residual flow 50% of Q7,10 equal to 3,1137 m³/s. This study can serve as a basis for future research and technical work on environmental support capacity in similar hydrographies.